Based on observation, I would guess: - Alien megastructures visible at long distances are plausibly not a thing, due to material limitations or something. - B

Based on observation, I would guess: - Alien megastructures visible at long distances are plausibly not a thing, due to material limitations or something. - But, even very slow expansion into space should have covered the galaxy long ago, so the aliens should be here or in the archaeological record. A possible explanation for the latter is, what if the aliens are everywhere but they don't go near stars? Once you have a kind of generation ship that can function essentially forever in interstellar space, why would you risk going near a star or whatnot? That would also be consistent with the "dark forest" viewpoint.